Five years on, we've learned nothing from the largest onshore oil spill in U.S. history

Five years ago, in the middle of the night, an oil pipeline operated by Enbridge ruptured outside of Marshall, Michigan. It took more than 17 hours before the Canadian company finally cut off the flow, but by then, more than a million gallons of tar sands crude had oozed into Talmadge Creek. The oil quickly flowed into the Kalamazoo River, forcing dozens of families to evacuate their homes. Oil spills of that magnitude are always disastrous, but the Kalamazoo event was historically damaging.

The first challenge was the composition of the oil. Fresh tar sands crude looks more like dirt than conventional crude—it’s far too thick to travel through a pipeline.

To get this crumbly mess to flow, producers thin it out with the liquid constituents of natural gas. Diluted bitumen, or dilbit, as it’s called in the tar sands industry, is approximately three parts tar sands crude, one part natural gas liquids.

When dilbit gushed into Talmadge Creek in 2010, the mixture broke apart. The volatile natural gas liquids vaporized and wafted into the surrounding neighborhoods. The airborne chemicals were so difficult to find and eliminate that Enbridge decided it would be better to simply buy some of the homes that were evacuated, preventing the residents from ever returning.

The tar sands oil, which stayed in the water, presented an even bigger chemistry problem. Most forms of oil, including conventional crude, are less dense than water. That’s why oil makes such pretty colors when dropped into a rain puddle—it floats and plays tricks with the sunlight. Traditional oil spill cleanup technology relies heavily on this density relationship. Skimmers and vacuums remove it from the surface. Floating booms prevent surface-level oil from moving into environmentally sensitive areas.

Tar sands crude behaves differently. “Tar sands bitumen is a low-grade, heavy substance,” says Anthony Swift, director of NRDC’s Canada Project (disclosure). “Unlike conventional crude, when bitumen is released into a water body, it sinks.” (See “Sink or Skim,”onEarth’s infographic on why tar sands oil is more difficult to clean up than conventional crude.)

Put simply, the spilled dilbit traveled in every direction—into the air, with the current, to the bottom of the river—at the same time. The U.S. Environmental Protection Agency’s indisputably naïve response reveals how little anyone knew about tar sands crude. The EPA demanded that Enbridge remove the oil from wetlands surrounding the pipe by August 27, a little more than one month after the spill began. The agency wanted the stuff out of the creek, river, and shorelines by the September 27. Those deadlines would have been practical for a typical spill—but not for a tar sands oil spill. A half-decade later, some of the oil still remains—though, much of that has to do with Enbridge botching the cleanup effort (see onEarth’s three-part series, “The Whistleblower”).

Enbridge’s bungling began even before the spill. First, the company knew the pipeline was vulnerable by 2005, if not earlier. When the rupture finally came in July 2010, operators dismissed the alarms as a malfunction of the system for 17 hours before finally accepting that the pipeline had failed. Making things worse, six hours after Calhoun County residents were complaining to 911 about the smell of oil, Enbridge employees were still trying to fix the problem by pumping additional oil into the pipeline. In its review of the accident, the National Transportation Safety Board faulted Enbridge’s “culture of deviance” for what happened, pointing out that the response team in the first hours consisted of four local pipeline maintenance employees who were inadequately trained and made a series of bad decisions.